Laminate having textured wear surface of uniformly covered chips and recesses

ABSTRACT

A wear resistant laminate having a polymer-impregnated glass fiber substrate and a textured surface, the texture resulting from relieving stress in pre-stressed chips and the wear resistance resulting from the substantially uniform covering over the chips and the recesses of the textured surface.

FIELD OF THE INVENTION

The present invention relates to decorative laminates that are suitableas surface coverings for floors, walls, etc., and, more particularly,the invention is directed to a decorative laminate having surfacetexture for improving the wear resistance of the laminate.

BACKGROUND OF THE INVENTION

Decorative laminates used as surface coverings for floors are well-knownin the art and have achieved broad use in both domestic and commercialenvironments. These laminates in the form of sheet material composed ofa resinous polymer composition, e.g., polyvinyl chloride, laminated to asuitable substrate, e.g., a fibrous backing sheet, have been used formany years as sheet flooring. To illustrate, many methods and processessuch as mechanical embossing, chemical embossing or inlaying have beenutilized to provide contrasting surface finishes and thereby impartdecorative effects to the sheet flooring. For example, U.S. Pat. Nos.3,000,754 and 4,456,643 each discloses different techniques or means formaking floor covering products such as floor tiles or sheet flooringhaving decorative surface effects. A goal common for all these productsis to combine attractive surface decorative effects from an aestheticviewpoint with substantial wear resistance from a functional standpoint.

In U.S. Pat. No. 3,000,754, the embossed effect is obtained by hotpressing at least two PVC resins of different molecular weights. Thehigher molecular weight resin has a greater tendency to relax in adirection normal to the plane of the surface covering to provide thetextured effect.

In U.S. Pat. No. 4,456,613, the laminate has an embossed surfacecomposed of raised segments containing PVC particles adjoining recessedsegments devoid of PVC particles. Similar articles are disclosed in U.S.Pat. Nos. 4,599,264 and 4,450,194.

In U.S. Pat. No. 4,405,657, a non-skid plastic floor covering isdisclosed wherein slip-resistant particles are embedded in a curedplastic matrix with the uppermost layer of particles protruding from thematrix. A clear or translucent wear layer coats the outer surface.

U.S. Pat. Nos. 4,816,317 and 4,816,319 disclose the use of discreteportions of a thixotropic plastic material containing solid material toprovide the raised elements of the textured surface.

U.S. Pat. No. 4,348,447 discloses a non-skid plastic flooring product inwhich inorganic particles are applied to the adhesive surface of aplastic matrix and then embedded into the matrix by pressure. However,particles applied in this manner do not penetrate uniformly throughoutthe matrix. Furthermore, to obtain complete bonding of the particles tothe plastic matrix, a thin coating is applied over the surface. Thisstep tends to fill the interstitial areas between raised particles andreduce the textured effect on the surface. The use of such particlesalso tends to obscure any underlying decorative portion that may beimposed on a substrate that supports the plastic matrix containing theparticles.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a decorativelaminate having a textured wear surface that avoids the difficultiestypically associated with the use of particles that are pressed into thesurface of the laminate.

It is also an object of the present invention to provide the texturedwear surface in a cost-effective process that minimizes the requiredsteps while still insuring success.

According to the present invention, there is provided a decorativelaminate having a textured wear surface suitable as a floor or wallcovering comprising:

1) a substrate, optionally having a printed image thereon, comprising aglass fiber layer impregnated with a synthetic organic polymer;

2) a layer of a substantially transparent synthetic organic polymersuperimposed on the substrate and preferably adhered or bonded to thesubstrate; and

3) a plurality of polymeric chips distributed throughout and embedded inthe organic polymer layer, the chips having been stressed prior toembedding and relaxed thereafter to provide a textured effect to thesurface of the laminate.

Specifically, the polymeric chips, that are embedded in the organicpolymer layer, are "stress-induced" chips that have been stretchedlengthwise, while relatively solid after cooling from the molten stage,to an extent of at least twice its original length; and then, afterbeing embedded or at least partially embedded, laid flat in the softorganic polymer layer and coated, the stressed chips are permitted torelax or contract, usually by heating the structure at or above theoriginal stretching temperature but below the melting temperature of theorganic polymer. During the heating, the chips tend to contract or "pop"to provide the desired textured effect on the surface of the productwhile still remaining coated with the wear resistant polymeric coating.

To insure that all chips are completely embedded in the polymeric layerbefore the heat treatment, it is recommended that a thin coatingcompatible with the polymeric layer (usually the same composition as thepolymeric layer) be applied over the chips prior to relaxing to protectthem and the surface of the structure from wear and dirt and also tofill any potential dirt-collecting recesses that may have developedduring the production process.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a cross-sectional view depicting the arrangement of elementsand structural features of the product of the invention;

FIG. 2 is a schematic view of the process and equipment for theproduction of the "stress-induced" polymeric chips used in the processof the invention; and

FIG. 3 is a schematic view of the process and equipment used in themanufacture of the product of the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 depicts the decorative laminate product 10 of the invention incross-section. The laminate is composed of three basic layers: the backcoat layer 16, the substrate layer 11 and the surface or wear layer 18that includes the texture-producing chips 14 embedded therein. Anoptional layer 12 composed of a thin clear coat of plastisol may beapplied to the surface of the substrate layer 11 if the surface isprinted with rotogravure or other printing techniques that impart colorand pattern to the product.

The substrate 11 is preferably a glass fabric impregnated and coatedwith a plastisol to seal the glass fibers. The substrate 11 comprisesanywhere from 10 to 30 mils of the approximately 80-100 mils thickproduct.

It should be understood that any of the substrates normally employed inthe surface covering field may be employed to prepare the laminate ofthis invention. It should be a strong, durable and flexible material.Thus, any woven, felted or solid sheet of 1. synthetic or naturalmaterial may be used as substrate 11.

Since substrate 11 in the figure is an impregnated glass mat, it isusual to provide one or more seal or back coats 16 to a thickness ofabout 25-35 mils. This coat 16 is conveniently applied in the form of anaqueous emulsion of resinous binder and, optionally, filler. Theresinous compound is preferably a vinyl resin.

The surface or wear layer 18 is usually, although not necessarily,applied in two steps; one step before the particles 14 are deposited andthe optional second step after the particles 14 are deposited. The wearlayer 18 may be anywhere from 20 to 40 mils thick, usually about 25 to30 mils; and the chips 14 are from 2-20 mils in their shorter dimension,usually about 10 mils thick.

The resin component of the back coat 16, the wear layer 18, and theparticles 14 is preferably a vinyl resin, that is, a polymeric materialobtained by polymerizing compounds containing at least one --CH═CH₂radical. Useful vinyl resins include homopolymers, such as polyvinylchloride, polyvinyl acetate, polyvinyl propionate, polyvinyl butyrate,polymerized vinylidene chloride, polymerized acrylic acid, polymerizedethyl acrylate, polymerized methyl acrylate, polymerized propylacrylate, polymerized butyl acrylate, and the like; copolymers of theabove with each other such as vinyl chloride-vinyl acetate copolymer,vinylidene chloride-vinyl chloride copolymer, methyl methacrylate-vinylchloride copolymer, methyl acrylate-ethyl acrylate copolymer, ethylacrylate-butyl acrylate copolymer, and the like and copolymers of theabove with other monomers copolymerizable therewith, such as vinylesters, including vinyl bromide, vinyl fluoride, vinyl choroacetate,vinyl alkyl sulfonates, trichloroethylene and the like; vinyl etherssuch as vinyl ethyl ether, vinyl isopropyl ether, vinyl chloroethylether and the like; cyclic unsaturated compounds such as styrene,chlorostyrene, coumarone, vinyl pyridine and the like; maleic andfumaric acid and their derivatives such as diethyl maleate, dibutylfumarate and the like; unsaturated hydrocarbon such as ethylene,propylene, butylene and the like; allyl compounds such as allyl acetate,allyl chloride, allyl ethyl ether, and the like; conjugated andcross-conjugated unsaturated compounds such as butadiene, isoprene,chloroprene, 2,3-dimethylbutadiene-1,3, divinyl ketone and the like. Themonomers listed hereinabove are useful in preparing copolymers with avinyl resin and can be used as modifiers in the polymerization, in whichcase they may be present in an amount of a few percent, or they can beused in larger quantities, up to as high as 40 percent by weight of themixture to be polymerized. If desired, a mixture of vinyl resins can beused in preparing the layer 18 for use in the invention.

A plasticizer for the vinyl resin is also frequently present in thesecompositions. Suitable plasticizers for the vinyl resin include estertype plasticizers such as tributyl phosphate, dioctyl phthalate,dipropylene glycol dibenzoate, phenyl phosphate, dibutyl tartrate, amyltartrate, butyl benzyl benzoate, dibutyl sebacate, dioctyl adipate,didecyl adipate and the like, rubbery plasticizers, such asbutadiene-styrene copolymer, butadiene-acrylonitrile copolymer, and thelike, and other materials which function as plasticizers, such asepoxidized drying oils, aromatic hydrocarbon condensates and the like.Where certain flexible soft vinyl resins are used in formulating theselayers, such as polymers containing large proportions of ethyl acrylate,no plasticizer is needed. However, in most instances, a plasticizer isessential in order to impart the necessary properties of flexibility tothe dried film.

Likewise, plastisol or organosol dispersions of vinyl resins can beutilized for seal coats on one or both surfaces of substrate 11.

The thickness of the relatively flat, fibrous substrate 11 will dependto a large extent upon the particular product to be made and theparticular subsequent use for which it is intended. Normally, athickness in the range of from about 10 mils to about 90 mils issatisfactory.

The chips 14 are prepared by the process shown schematically in FIG. 2.Specifically, a polymeric film 21, about 10 inches wide and anywherefrom 30-40 mils thick, preferably about 40 mils thick, is extrudedthrough the die 22 of a standard melt extruder, not shown. The film 21is cooled to a temperature just above its glass transition temperature(about 50° C.) by passing over a conventional, cooled calender roll 23and then the film is drawn to about one-fourth its original thickness bypassing through the nip of roll 23 and stretching roll 24. The stressedfilm is then led to a slitter, grinder or dicer 25 and sieve 26 toprovide "stressed" particles or chips. A typical distribution ofstress-induced chips is shown in Table 1 below.

                  TABLE 1                                                         ______________________________________                                                  Particle Size   % Retained                                          Sieve #   Inch        Micron  on Screen                                       ______________________________________                                        14        .0555       1410     3                                              20        .0331       840     64                                              25        .0278       706     14                                              50        .0117       297     18                                              ______________________________________                                    

The chips 14 are usually formulated from polyvinyl chloride havingK-values (related to molecular weight, which in turn determines meltcharacteristics) in the range of 53-73. Resins outside this rangeperform marginally. If the K-value is above the preferred range, thetemperature necessary to melt the resin for extrusion may causedegradation of the polymer. If the K-value is below the range, the"stressed" chips tend not to recoil during the relaxation step. If thechips 14 are formulated from the same polymer as constitutes thepolymeric layer 18, the polymer of the chips 14 would have a highermolecular weight than the polymer of layer 18, to enable the chips 14 to"pop" within the softened layer 18 and produce the textured effect. Ithas been noted that the chips 14 in the textured surface of the productof the present invention tend to display curved or rounded edges whencompared to the sharp edged chips that provide the textured surface ofprior art products.

A decorative printed image 12 may be applied to the substrate 11 on thecoated surface thereof after drying the coating. Printing isconventional and paints and inks normally used for application of adecorative design to a vinyl film or layer are used. The composition ispreferably formulated so that the binder of the ink contains anappreciable quantity of a vinyl resin. Suitable vinyl resins includevinyl chloride polymer, vinyl chloride-vinyl acetate copolymer, vinylchloridevinyl propionate copolymer, vinyl butyrate polymer, vinylidenechloride polymer, vinylidene chloride-vinyl chloride copolymer,copolymers of vinyl chloride and vinylidene chloride with esters ofmaleic and fumaric acid, such as dimethyl, diethyl, and dibutyl maleateand fumarate, and the like. Extender resins, such as nitrocellulose oracrylic polymers, can be employed as a portion of the binder of the inkor paint.

The decorative printing composition contains pigments according to thecolors desired and is preferably formulated as a solution in the solventsuch as cyclohexanone, methyl ethyl ketone, methyl isobutyl ketone andthe like.

The decorative printing composition can be applied to the seal coatedsurface of the sheet in any way appropriate for producing the particulardecoration desired. Any of the rotary graphic art printing processes,such as rotogravure, offset printing or lithography, can be used. Ifdesired, the design can be applied by conventional block printingtechnique.

In FIG. 3, a schematic view of the process of this invention, thesubstrate or backing sheet 11, specifically a saturated-glass substrate,that has been impregnated and hot pressed to form a substantially smoothsurfaced sheet, is fed through the nip and around the cylindrical rolls31 and 32 of an Ulbricht reverse roll coater. The clear viscous liquidplastisol layer 18 is applied to the top surface of the backing sheet 11to a thickness of 5-60 mils, preferably about 20-30 mils and the coatedsheet is passed beneath the outlet of a Shilling feeder 33 containingthe specially-prepared, stressed chips 14. The chips 14 are deposited ata rate of about 40 grams/square foot into the plastisol layer 18 inaccordance with a predetermined pattern set on the Shilling feeder 33.

The combination of base layer 11 and top layer 18 containing theparticles 14 is then led over a heated drum 34 maintained at atemperature of about 320° F. The primary purpose of this step is toinsure that substantially all particles 14 will be in a prone position,i.e., in a substantially horizontal plane. The time of exposure to thistemperature is selected to cause the particles 14 to become permanentlyfixed in position. As the gelled substrate of layers 11 and 18, thelatter containing the prestressed particles 14, leaves the drum 34, thetop surface of the laminate 10 is almost smooth.

After passing through the cooling rolls 35, 36 and 37, the gelledlaminate 10 may be further clear coated with a second application of theplastisol used to prepare layer 18 at the Waldron reverse roll coatershown at 38. The sheet is then passed into the oven 39 maintained at atemperature above which the extruded polymeric film was originallystretched but below the melting temperature of the polymer. Thisexposure permits the chips to become substantially unstressed and tendto return to approximately their original dimensions. In so doing, thechips 14 tend to "pop" as shown in FIG. 1 and provide the laminate withthe desired textured surface. The second application of plastisol tolayer 18, although not always necessary, assures that the particles inthe substantially unstressed condition will be completely coated andalso that any recesses in the final product are filled to prevent unduesoiling. The laminate is then permitted to cool and, thus, provide thetextured surface covering product of this invention.

What is claimed is:
 1. A wear-resistant product having a texturedsurface comprising:(a) a glass fiber substrate impregnated withpolyvinyl chloride; (b) a layer of a synthetic organic polymer ofpolyvinyl chloride superimposed on said substrate; and (c) a pluralityof chips of polyvinyl chloride having a K-value of 53-73 distributedthroughout and embedded within said organic polymeric layer, said chipsof polyvinyl chloride having a higher K-value than the polyvinylchloride of said layer of synthetic organic polymer having been stressedprior to embedding and having been relaxed after embedding to provide atextured, wear-resistant surface of said chips and recesses betweenchips, said surface being characterized by a polymeric covering ofsubstantially uniform thickness over both said chips and said recesses.2. A produce as in claim 1 wherein said substrate is 10-30 mils thick,said superimposed layer is 25-30 mils thick and said chips are each 2-20mils thick.
 3. A product as in claim 1 in which a back coat issuperimposed or coated on the surface of said substrate opposed to thesurface on which the layer containing the chips is superimposed.
 4. Aproduct as in claim 1 wherein a decorative image is applied to at leastone surface of said substrate.